Upon your arrival in the terminal area, ATC either
clears you to a specific altitude, or they give you a "descend via" clearance that instructs you to follow
the altitudes published on the STAR. [Figure 4-21 ]

You are not authorized to leave your last assigned altitude
unless specifically cleared to do so. If ATC
amends the altitude or route to one that is different
from the published procedure, the rest of the charted descent procedure is canceled. ATC will assign you any
further route, altitude, or airspeed clearances, as necessary.
Notice the JANESVILLE FOUR ARRIVAL
depicts only one published arrival route, with no named
transition routes leading to the basic STAR procedure
beginning at the Janesville VOR/DME. Vertical navigation
planning information is included for turbojet and
turboprop airplanes at the bottom of the chart.
Additionally, note that there are several ways to identify
the BRIBE reporting point using alternate formation
radials, some of which are from off-chart NAVAIDs.
ATC may issue a descent clearance that includes a crossing
altitude restriction. In the PENNS ONE ARRIVAL,
the ATC clearance authorizes you to descend at your discretion,
as long as you cross the PENNS Intersection at
6,000 feet MSL. [Figure 4-22]

In the United States, Canada, and many other countries,
the common altitude for changing to the standard
altimeter setting of 29.92 inches of mercury (or 1013.2
hectopascals or millibars) when climbing to the high
altitude structure is 18,000 feet. When descending from
high altitude, the altimeter should be changed to the
local altimeter setting when passing through FL 180,
although in most countries throughout the world the
change to or from the standard altimeter setting is not
done at the same altitude for each instance.

For example, the flight level where you change your
altimeter setting to the local altimeter setting is specified
by ATC each time you arrive at a specific airport. This
information is shown on STAR charts outside the U.S.
with the words: TRANS LEVEL: BY ATC. When
departing from that same airport (also depicted typically
on the STAR chart), the altimeter should be set to the
standard setting when passing through 5,000 feet, as an
example. This means that altimeter readings when flying
above 5,000 feet will actually be flight levels, not
feet. This is common for Europe, but very different for
pilots experienced with flying in the United States and
Canada.